# Aquarium airline tubing and fittings: 3/16 in vs 4 × 6 mm, check valves, connectors and Luer barb match

> What size is aquarium airline tubing, and do check valves and fittings take 3/16 in or 4 mm tube?

- Category: Tri-clamp & pipe › Pipe, tube & threads
- Kind: Standard part
- Basis: retailer and maker listings read (Bluviva, Perfect Ponds & Koi, Lee's, Aquaneat, Penn Plax); only the tubing ID and OD are printed, no fitting dimensions
- Page: https://xemstudio.com/objects/aquarium-airline-tubing/ · JSON: https://xemstudio.com/api/geometry?object=aquarium-airline-tubing · Plain text: https://xemstudio.com/objects/aquarium-airline-tubing/sheet.txt
- License: dimension sheet CC BY 4.0 (Xem Studio); files CC BY 4.0 or their publisher's license
- Use in every chat: add https://xemstudio.com/mcp as a connector (https://xemstudio.com/use-with-ai/)

**Exact dimensions.** True size, with no tolerance added.

## Notes

- Two sizes are sold as standard airline tubing: 4 mm ID × 6 mm OD (metric listings) and "3/16 in" (US listings). The 4 mm and 3/16 in (4.76 mm) are not the same number, and the US listings read here do not print the OD of their 3/16 in tube, so the page does not claim the two are interchangeable; the 3/16 in value is the tube's nominal size, and Lee's calls it the ID of the tube its check valve takes.
- Fittings (check valves, 2- and 3-way valves, L- and T-connectors, splitters) are listed as 'for 3/16 in' or 'for 4 mm' tubing. No listing read prints a barb diameter, length or port size for these parts, so there are no fitting dimensions here and no files.
- A Luer barb that fits this tube: the nearest sizes in Nordson's and Qosina's tables are 5/32 in (4.0 mm ID) and 3/16 in (4.8 mm ID) tube barbs, see luer-to-barb-adapters. Silicone and PU push-fit tube sizes (including the 4 × 6 mm tube) are on silicone-tube-and-fittings.
- Not covered: pump outlet nozzle diameters, air-stone barbs and CO2 tubing, which were not read.

## Sizes

| item | ID | OD | wall | source |
|---|---|---|---|---|
| airline tubing, metric | 4 mm | 6 mm | about 1 mm (computed, (OD − ID)/2) | Bluviva ("4/6 mm" as the usual size for most air pumps and attachments); Perfect Ponds & Koi (4 mm ID, 6 mm OD) |
| airline tubing, "3/16 in" | 3/16 in (4.76 mm, computed) | not printed | not printed | Aquaneat listing: "Standard 3/16 in" tubing; Penn Plax listing: "3/16 in" (no ID/OD split in either); Lee's: pumps that use 3/16 in ID tubing |
| L-shaped connector | for 4 mm ID tubing | — | — | Aquaneat listing (no part dimensions printed) |
| air control valve (2-way / 3-way) | for 4 mm tubing, or "3/16 in ID" | — | — | Aquaneat listings (no part dimensions printed) |
| check valve | for 3/16 in airline tubing | — | — | Lee's 12405, Aquaneat and other listings read (no part dimensions printed) |

## Where the files are

- Bluviva: [Airline and fittings category: standard airline tubing 4/6 mm (ID/OD); fittings should match the tubing](https://bluviva.com/product-category/equipment/aeration/airline-fittings/) — web — Retailer page; numbers only
- Perfect Ponds & Koi: [H/D clear per meter airline 4 mm ID, 6 mm OD](https://www.perfectpondsandkoi.co.uk/products/per-meter-airline-h-d-clear-4mmid-6mm-od) — web — Retailer page; numbers only
- That Pet Place (Lee's check valve 12405): [Lee's airline check valve: all air pumps that use 3/16 in ID tubing](https://www.thatpetplace.com/check-valve-1pk_2) — web — Retailer page; numbers only
- Walmart listing (Aquaneat airline tubing): [Standard 3/16 in airline tubing; check valves for 3/16 in tubing; L-shaped connectors and air control valves for 4 mm ID tubing](https://www.walmart.com/ip/Aquaneat-Aquarium-Airline-Tubing-40Feet-Standard-3-16-Tubing-for-Air-Pump/541130335) — web — Retailer listing; numbers only

## Questions

**What size is standard aquarium airline tubing?**

Retailers list 4 mm ID × 6 mm OD (metric) and 3/16 in nominal (US). The US listings read do not print an OD.

**Does a 3/16 in check valve fit 4 mm tubing?**

The listings say 3/16 in valves are for 3/16 in tubing and some connectors are for 4 mm ID tubing; no listing prints the valve's barb size, so test the fit on your own tubing.

## Fits with

- [Silicone tube 1 × 3 to 10 × 14 mm (ID × OD)](https://xemstudio.com/objects/silicone-tube/)
- [Luer lock and Luer slip to barb adapters: tubing ID sizes 1/16 to 1/4 in (Nordson Value Plastics, Qosina), male and female](https://xemstudio.com/objects/luer-to-barb-adapters/)
- [Luer connectors (ISO 594 / ISO 80369-7): 6% taper dimensions, male and female Luer slip and Luer lock, + true-size taper gauges](https://xemstudio.com/objects/luer-connectors-iso-594-80369-7/)
- [90° elbow for 4 × 6 mm tube](https://xemstudio.com/objects/transfer-elbow-4mm/)
- [Drip irrigation tubing sizes: 1/8, 1/4 and 1/2 in poly tubing, ID x OD (0.170 x 0.250, 0.600 x 0.700 in)](https://xemstudio.com/objects/drip-irrigation-tubing-sizes/)
- [Tri-clamp × hose barb adapters (14MPHR style): ½ to 4 in clamp, ¼ to 4 in hose](https://xemstudio.com/objects/tri-clamp-hose-barb-adapters/)
- [Tygon vinyl tubing (E-3603 / S3 E-3603): ID × OD × wall, 1/32 to 1 in ID, 1/16 to 1/4 in walls](https://xemstudio.com/objects/tygon-vinyl-tubing-e-3603-sizes/)